This invention relates to an electrical connector for a coaxial flat cable used for an electronic appliance, and more particularly to a multicontact connector which operates with high transmission efficiency and less crosstalk.
With development of electronics, electronic circuits used in electronic appliances have been designed to pass low voltage and small electric current or high frequency current. Under such circumstances, small diameter coaxial cables have been widely used for connection between electronic appliances or between circuit boards thereof.
Coaxial flat cables have been used for connecting electronic appliances or circuit boards thereof. In general, a coaxial flat cable includes a plurality of small diameter coaxial cables arranged in a flat plane, and a sheath applied onto the outside of the arranged coaxial cables. Each of the small diameter coaxial cables consists of a center conductor of a 0.1 mm to 0.5 mm diameter and an outer conductor of a 0.5 mm to 0.8 mm diameter. In connection between circuit boards or between electronic appliances, the flat cable is connected to the circuit boards or electronic appliances through connectors for the coaxial flat cables.
FIG. 1 illustrates a typical one of multi-contact connectors which have been widely used for this purpose. In FIG. 1, the multicontact connector includes a receptacle connector 2 and a plug connector 5 adapted to be fitted in the receptacle connector 2. The receptacle connector 2 is attached to a circuit board 1. The plug connector 5 has connection terminals 3 arranged in a flat plane in consideration of connection with a flat cable. The flat cable includes a plurality of coaxial cables 8 arranged in a plane and having conductors 7. Reference numeral 4 indicates a ground bar.
FIG. 2a is a perspective view illustrating a conventional arrangement of contacts of the multi-contact connector. In FIG. 2a, each of the contacts 3 is composed of a connection terminal A to be connected to one of coaxial cables of the flat cable, a fixing portion B to be held in the insulating body of the plug connector, and a contact portion C to be brought into contact with one contact of the receptacle connector.
The references S.sub.1, S.sub.2, . . . S.sub.5 and S.sub.6 and G.sub.1, G.sub.2, . . . G.sub.5 and G.sub.6 on the contact 3 are intended to designate signal contacts for signals and ground contacts for grounding, respectively. The signal contacts are connected to the center conductors of the coaxial cables, respectively, for signals, while the ground contacts are connected to the outer conductors of the coaxial cables, respectively, for grounding. The numbers of suffixes correspond to the numbers of the coaxial cables of the flat cable to be connected thereto. For example, the signal contact S.sub.1 is connected to the center conductor of the first coaxial cable of the flat cable, and the signal contact S.sub.2 is connected to the center conductor of the second cable of the flat cable. On the other hand, the ground contact G.sub.1 is connected to the outer conductor of the first coaxial cable of the flat cable, and the ground contact G.sub.2 is connected to the outer conductor of the second coaxial cable of the flat cable.
The connection terminals A of the contacts 3 are arranged in the order of G.sub.1, S.sub.1, G.sub.2, S.sub.2, . . . G.sub.5, S.sub.5, G.sub.6 and S.sub.6 as shown in FIG. 2b viewed from the side of the connection terminals A. On the other hand, the contact portions C of the contacts 3 are regularly arranged that the signal contacts are in one or upper row as S.sub.1, S.sub.2, . . . S.sub.5 and S.sub.6 in the order of the suffixes and the ground contacts are in the other or lower row as G.sub.1, G.sub.2, . . . G.sub.5 and G.sub.6 in the order of the suffixes as shown in FIG. 2c viewed from the side of the contact portions C.
When a flat cable including coaxial cables is used for connection between electronic appliances and between circuit boards of electronic appliances, crosstalk can be reduced, for example, by approximately 50% in comparison to that of a usual flat cable having a plurality of coated conductors arranged in parallel with one another (in comparison with a transmission cable).
Although such a significant effect can be accomplished by the coaxial flat cable, more decrease of the crosstalk has been expected in the existing circumstances in that the electronic appliances have been required to be more multiple and to be operated at higher speeds.